Present day commercial refrigeration systems typically employ a two-phase cycle with a refrigerant that alternates between gaseous and liquid states. The systems utilize refrigerants such as Freon or R-134a to provide large cooling capacities. The refrigerant cycle for these systems include the use of a compressor, an evaporator, a condenser and expansion device and numerous refrigerant hoses. Such systems require a closed piping circuit to isolate the pollutional refrigerant from the environment. Further, these refrigeration systems at their end transfer heat through air or another gas, and hence require both a primary cooling medium, i.e. the refrigerant, and a secondary cooling medium, i.e. the air that transfers the heat from the object to be cooled. Not only are these systems expensive and require stringent containment of the refrigerant, the refrigerant level must also be monitored and refilled during the life of the system.
Open air-cycle air conditioning systems, also known as a Brayton cycle system or open reverse Brayton cycle, are known. With such a system the air (or another gas) itself is the working medium in the refrigeration cycle, and there is no need for a special refrigerant that is cycled through the system. Unfortunately, the air-cycle air conditioning system typically has a very small cooling capacity in comparison with a conventional refrigerant based system. These open air-cycle air conditioning systems are employed mainly in airplanes, where there is a ready availability of compressed air which can be tapped directly off the main engine super charger or jet engine compressor. Unfortunately, in stand alone refrigeration systems there is no such supply of compressed air, and hence the small cooling capacity in combination with a low overall efficiency or coefficient of performance (COP) of open air-cycle for refrigeration systems have made them commercially impracticable. Accordingly, there exists a need to provide a commercial refrigeration system for conditioning air utilizing an open air-cycle air conditioning system.